I agree, I think the lack of perks was surprising considering the impression I was given prior to purchasing. Particularly when I read about access to the private group, maybe I imagined it, but I kind of thought all along it would give me access to some actual content. However, both the private forum and the discord group are pretty bare. The only perk I saw was early access to HB3, and that was just 1 day early.
Perhaps early access to some of the HB3 features that haven't rolled out to public yet?...such as legion dungeon scripts as they are being worked on. Maybe they could share their pre-release internal builds after patches? I'm sure plenty of legendary folks would be more than happy to help with testing.